Modern agriculture, including silviculture, often requires planting of large numbers of substantially identical plants that are genetically tailored to grow optimally in a particular locale or to possess certain other desirable traits. Production of new plants by sexual reproduction can be slow and is often subject to genetic events resulting in variable traits in its progeny. As a result, asexual propagation has been shown to yield large numbers of genetically identical embryos for some species. Such embryos are typically further cultured under laboratory conditions until they mature into an autotrophic “seedling” state characterized by an ability to produce their own food via photosynthesis, to resist desiccation, to produce roots able to penetrate soil, and to fend off soil microorganisms.
Researchers have experimented in asexual propagation with the production of artificial seeds known as “manufactured seeds.” Manufactured seeds typically include the following components: a seed shell, a synthetic gametophyte, and a plant embryo. A manufactured seed that does not contain a plant embryo is known in the industry as a “seed blank.” The seed blank is typically a cylindrical capsule made from biodegradable plastic having an open end and a closed end. Manufactured seeds are produced by placing the synthetic gametophyte within the seed shell such that it substantially fills the interior of the seed shell. A longitudinally extending hard porous insert, known in the industry as a “cotyledon restraint,” may be centrally located within the synthetic gametophyte. The cotyledon restraint includes a centrally located cavity extending partially through its length and is sized to receive the plant embryo. The plant embryo is approximately 4 to 7 millimeters in length and roughly 0.5 millimeters in diameter. The shape of the plant embryo is somewhat cylindrical, but is also irregular in cross-section and varies in diameter along its length. The plant embryo may contain both a radicle (or root) end and a cotyledon end. The plant embryo is deposited into cavity of the cotyledon restraint oriented so that the cotyledon end is inserted first. Subsequently, the plant embryo is typically sealed within the seed shell using at least one end seal.
Numerous types of plant embryo delivery systems have been used to transfer the plant embryo through the manufactured seed production line. Examples of such systems include U.S. Pat. No. 6,684,564, U.S. Pat. No. 7,207,139, and U.S. Pat. No. 7,603,807, all of which are hereby incorporated by reference. Although known systems have been effective in transporting plant embryos, problems are often encountered. For example, in some applications, embryos are hydrated to prevent damage from desiccation. These moist and sticky embryos often remain attached to plant embryo delivery systems and may be damaged during removal attempts. Even if the embryo is not damaged, sticking can also cause improper orientation or placement in the seed shell. Either scenario results in the possibility of wasting viable embryos, which is costly in commercial applications. Accordingly, there is a need in the industry to develop new systems and methods for embryo insertion into manufactured seeds.